Automatic choke mechanism



y 9, 1944. c. H. JORGENSEN ,348,544

AUTOMATIC CHOKE MECHANISM Original Filed Dec 30, 1935 s Sheets-Sheet 1 INVE NTOR CLARENCE H.JOR6EN5EN ATTORNEY May 9, 1944.

C. H. JORGENSEN AUTOMATIC CHOKE MECHANISM riginal Filed Dec. 50, 1935 3 Sheets-Sheet 2 'INVENTOR CLARENCE. H.Jo\zeEN$l-:N

ATTORNEY v Patented May 9, 1 94 4 AUTOMATIC CHOKE MECHANISM Clarence H. Jorgensen, Anderson, 11111., assignor to General Motors Corporation, Detroit, Mich, a corporation ofrDelaware Continuation of application Serial No. 56,605,

December 30, 1935. This application October 23, 1939, Serial No. 300,838 a 33 Claims. (Cl. 123 119) V This invention relates to automatic devices for controlling the ratio of fuel to air in the co-m-" to that type of mixture proportioning device which is controlled jointly by the operation of suction operated means and a thermally responsive device the effect of which varies 'as the engine tem perature varies.-

This application is a continuation of application Serial No. 56,605, filed December 30, 1935.

A device of the general type described above is shown in the prior application of C. H. and P. J. Jorgensen, Serial No. 585,510, filed January 8,- 1932, in which the mixture ratio is controlled during various operating conditions by the position of a valve in the air inlet of the carburetor which regulates the admission of air thereto, thus producing a mixture high in fuel content when the valve approaches closed position, and a mixture of less fuel content proportionally when the valve moves to a more nearly open position.

In the earlier joint application referred to, this air inlet valve is of the unbalanced type which the flow of air tends to open, is held in closed position by a spring and by the added eifect of a thermostat when the engine temperature is relatively low, 'the thermostat acting to move the valve toward open position as the thermostat ex pands upon increase in engine temperature when way a rich mixture is provided for cold starting and a leaner mixture for normal running conditions. l

Means are also provided in the earlier application for securing the admission of air in progressively increasing quantities, in the event of pro- ,longed cranking of the engine without starting,-

so as to prevent flooding, and means is also dis- .closedin the earlier application which is operable fold vacuum which is communicated to such cylinder through a valve controlled conduit, while the 'closing of the air valve upon acceleration is brought about by the action of asuction. con

the engine operates under its own power. In this trolled piston hereinafter .termed a kicker pis-r ton which upon reduction of suction in the in-: take pipe, following an opening movement of the throttle, is moved by a spring to force the air inlet valve toward closed position against the pressure exerted by the air entering the carburetor.

Attention may be called to the fact that; although a piston is shown in the earlier case, a means may be used as a substitute for the master piston) l I i It is the general object of thepresent invention to provide certain specific improvements in the device disclosed in the earlier application so as to improve its action in certain particulars which will be apparent from the more specific description of the invention which appears later and to enable the device to more accurately control the proportioning of the mixture under the many different operating conditions which are met in actual service. More specifically, one feature of the invention consists in the mounting of the choke controlling unit with the thermostat therein directly on the manifold hot spot tofacilitate the heating of the thermostat and the provision of a suction con-' duit'extending directly fromvthe wall of the controlling. unit through the wall of the hot spot into, the intake passage, to prevent the necessityofithe use of flexible tubing to form the suction conduit A further feature of the invention consists in the provision of a copper or other metallic gasket between the choke controlling unit and the mania 7 fold, which serves asa direct conductor of heat to apoint adjacent. the thermostat and is pro;-

vided with a portion whichextends partially or wholly around the thermostat to increase the heating effect on suchelement. 1

Another feature of this invention consistsl'in' the provisionof a check valve in the top of the piston operable to produce a richer mixture dure ing the acceleration period to prevent the movement by suction, of such piston in a direction to open the air inlet valve on increase of engine suction eifective on the piston, under certain conditions.

An additional feature'of the invention lies in the provision of means which may be manually adjustable for limiting the movement of the master piston or bellows due to suction so as to determine the position the thermostat assumes when the throttle is-partly open so that the fuel air ratio of the part throttle mixture may be variably con trolled. j v r A still further feature of the invention comprises a manually operable metering valve by means of which the suction conduit through which suction is communicated to the master piston from the engine may be controlled.

Another feature of the invention resides in the provision of means to prevent any fouling of the surface .of .this control .valve .by .deposits which may precipitate from the combustible mixture.

Another feature of the invention consists in the provision of a tapered bleed slot in the wall of the cylinder in which the kicker piston slides in order to variably control the actionof the piston.

in accordance with varying operating conditions and with varying positions of the choke valve when the opening movement ofthe throttle'beins.

A'further additional feature of .the invention resides in the provision of an improved form of operating connections between the master piston or bellows and the air inlet valve, in which the master piston is connected directly to the free and :to :generally improvethe idling operation under varying ltemperatures and other operating conditions.

An additional -specific improvement which forms afeature ofthis-invention comprises'a nut secured in the housing of the control unit in which one end of the=shaft to which thethermo- Stat1is' secured, :is journalled, which-nut is 'provided with a hub on which the idle stop which controls the closed position of the "throttle valve is "rotatablymounted; The purpose of this arrangemen-tis to prevent thepressureof the-throttle -closing spring treating friction' with respect to the shaft-to which the thermostat, is secured, which would have to be-overcomeby the thermostator the suctionoperated elements before such shaft-"could be'moved to transmittmotion to the airinlet'valve A still further 'fjeature of the'invention'in its preferred form as disclosed in the drawings of this application, resides in "the provision of a bellows which is 'operatedby suction'to control the position o'fthe mixture proportioning elementthroug'h the-'medium-of the'thermostat. While a ma'ster piston could'be employed, there are. certain specific advantages secured by'the use of a bellows which'will'be obvious "from'the detailed description of the device 3 illustrated, which appears=hereinafter.

Further objects 'andadvantages of the present invention will be apparent from the following description; reference'being had to the accompanying-"drawings wherein'a preferred embodiment of the present invention is clearly shown.

In thedrawings:

Fig, '1 is'a side elevation of .a charge forming unitandmanifold with which the'automatic choke mechanism which-constitutes the present. invention is incorporated.

f-Fig. 2 is a' plan 'viewof the 'choke controlling unit.

Figs. 3 and 4 are vertical sectional views through the'controluniton the lines 3'3 and '4-4 of Figf- 2.

Fig. 5 is a detailed elevation of a manually adjustable device for controlling the mixture ratio under part throttle operating conditions.

Fig. 6 is a detail view of the mechanism which is controlled by the-manually adjustable element showninl igb.

Fig. 7 is a detailed view showing ithe manner of mounting the cam which constitutes the idle stop for variably regulating the idling speed of the engine against certain temperature conditions.

fig. .8 is a detailed horizontal section showing the suction passage which communicates with one of the suction operated elements controlling the choke valve. I I

.Fig. 9 ,is a diagrammatic View of the charge .forming device with the control unit which con- Fig. 1.

Referring .most particularlytoQFigs. 1 and .9, the reference character 1.0 indicates ,in its .en-

tirety a carburetor of the conventional type which is secured to the riser l2 vof anintake manifold having a heating chamber or .hot spot 14 formed in its wall through whichexhaust gas is .adapted to be passed in the well known manner for the purpose of heating the ingoing charge .of-combustible mixture which is supplied to the engine. An attaching flange l6 isformed on .the carburetor by which it is secured to a cooperating flange 18 on the manifold in the conventional manner.

The carburetor is provided with an air-inlet 20 which is controlled by an air valve 22 of the unbalanced type, so that a blast of air entering the inlet tends to move said .valve to open position, the valve being normally held closed by a spring on the shaft 24 to which said valveissecured, the spring not being shown in the drawings. This valve restricts the admission of air to the carburetor and .in addition controls the pressure differential at the fuel nozzle to regulate the ratio of fuel toair inthe mixture which is supplied by the carburetor to the engine.

Fuel is .supplied through a fuel inlet pipep26 .to a float chamber 28 of "conventional form-and in which a constant level is maintained by-a valve to carried by float 32 and operating in the usual conventional manner. Fuel flows from the float chamber into the mixture passage through a fuel nozzle 3 which terminates substantially at the point of greatest suction 'in a Venturi tube 36 provided for the purpose of creating a high suction at the nozzle outlet as is customary in conventional carburetors. The flow of fuel from the nozzle may be controlled in any conventional manner as by a fuel valve or metering plug having a fixed orifice and a secondary fuel supply tube 33 may be provided to supply fuel'at a point between the'throttle'valve and the engine for idling as is the custom in conventional carburetors generally.

The flow of mixture from the carburetor to the engine is controlled by a throttle valve 69 secured to a shaft'Z journallcd in the carburetor housing in the usual way.

All of the foregoing construction is old, is shown in the prior joint application previously referred to and constitutes no part of the present invention, except insofar as the choke valve 22 is operated and controlled by the. automatic control unit which will presently be described and I in the detailed construction of which the present invention resides.

'The choke control unit is adapted to control the position of the valve 22 and in this manner to control the fuel air ratio of the mixture supplied to the engine. For this purpose the shaft 24 has secured to one end which projects beyond the carburetor housing an arm 44 which is connected pivotally to a link 48 connected pivotally to an arm'48 which is secured in any desirable manner to a shaft 50 which is joure nailed in the housing of the control unit in a manner hereinafter described and the movement of which shaft is controlled by. a thermally responsive element and suction operated the intake passage to the suction operated ele ments referred to, to regulate the position of the valve 22. Obviously the construction is such that rotation of the shaft 59 is transmittedto theshaft 24, the relative degree of rotation of these shafts, of course, depending on the length of thelever arms to wh ch link 45 is secured.

.To control the motion of the shaft 50 there isconnected at one end to such shaft a bimetallic thermostat 52 of the coil type, the free end of which is pivotally connected to a link M which at its upper end is connected to an ear 5E project-f ing from a plate 58 which comprises the lower 'end of a metallic or other bellows 50 received in a cylinder 6! formed in the housing 52 and closed at its lower end by a closure plate 62. The bellows is normally'held in its expanded position by a spring 63 which is positioned within the bellows, as clearly shown in the Fig. 9. The interior of the bellows 68 communicates with a suction passage 54 formed in the cover plate or the control unit and through which the suction ofthe intake manifold is communicated to the bellows, and which communicates with the horizontal suction passage 65 in which a tapered metering valve 558 is positioned as shown in l means, so that the position of said shaft is determined'by the temperature conditions, and the .degreeof suction-which is communicated from Fig. 3, which is manually adjustable to variably control the effective area of the suction passage which communicates with the bellows for a purpose more fully described hereinafterr Normally, when the engine temperature is low, and the various parts of the control device are relatively cold, such parts occupy the position shown inthe diagrammatic view of Fig. 9 with the valve 22 in closed position. Boththe thermostat, when the temperature is low. and the spring 53 within the bellows tend to hold the valve 22 closed and the force of these elements as well as the spring which is on the shaft 24 all tend to hold the valve closed when the temperature is low. The spring 63 holds the bellows in expanded position and determines the position of one end of the thermostatic coil. As the engine warms up the thermostat would, of course, expand, and this increase'in temperature and resulting expansion of the thermostat will cause a clockwise movement of the arm 48 so that the thermostat will assume a position at a higher temperature which would be effective to move the valve toward a partially open position. When the engine has fully warmed up the efiect of the thermostat would be to move the valve toward fully open position as the thermostatic coil continues to expand.

'' The action of the engine suction upon the bellows is utilized to move the air valve 22 to:- ward its open position in the event that the engine does not start to run within a relatively short time after the cranking of the engine begins and also to move the value still further toward open position when the engine is started cold and begins to run under its own power.

The engine suction is communicated through the suction passages previously described to the interior of the bellows as has already been set forth and the air within the bellows is slowly drawn out by action of this suction tending to contract the bellows and through the medium of the link 54 to pull upwardly on the free end of the thermostat and through the medium of the thermostat itself, to rotate the shaft 59 in a direction to move the arm 48 in a clockwise direction to effect opening of the valve 22. The metering valve 68 is designed to be positioned so that the effective area of the suctio passage is very small which results in a slow exhaustion of air from the bellows 62, the valve being manually adjustable so that it may be set to secure exactly the result desired. With this construction the bellows does not contract sufficiently to move the valve 22 toward open position until sufiicient time has elapsed for the engine to start normally, but it does contract sufficiently to ope the valve 22 if the cranking operation is prolonged. The contraction of the bellows will then pull the link upwardly enough to rotate the shaft 60 through the medium of the thermostat to move the valve 22 toward open position and admit air to the carburetor.

As indicated previously, this mechanism is provided in art for the purpose of preventing flooding in the event that the engine does not start in a very brief period after the cranking begins. If the valve 22 remains closed and no means were provided to open the valve toat least a partial extent as above described, the restriction of the air inlet would be so great that sufficient fuel would accumulate in the engine to cause flooding and make starting very difficult. By partially open ng the valve 22 in the event of failure to start within a comparatively brief time, this difliculty i prevented, as sufficient air is admitted to the engine cylinders to carry out the excess fuel which would cause the flooding referred to.

Of course, when the engine begins to run under its own power, there is a very considerable increase in suction in the intake passage at points between the throttle and the engine due to the sudden increase in the speed of movemnt of the engine piston which take place when the engine begins to run. At this time it is necessary that addit onal air be admitted to form a proper ly proportioned fuel mixture and the bellowsis designed to enable this admission of air'to be brought about. The increase of suction referred to is effective to further contract the bellows 62 and to move the valve 22 to a still further open position through the medium of the thermostat;

Necessarily. the time required for contraction of the bellows to accomplish the results just referred to varies somewhat under different conditions, not being the same in cold and hot weather, for instance. Also with varying fuels and because of the fact that engines vary in the degree of suction produced in the intake passage due towear and improperly seating valves and for other reasons, it is desirable to provide means for variably regulating the degree of suction communicated to the bellows to meet all of these variable conditions andfor-thispurposethe manually op- ..e-rable metering valve 1B8 hasbeen provided.

;By pmvision'of the-adjustable valve to time the 'QDBning-of the choke valve by action of suction, stalling of the engine is prevented' Such stalling --might otherwise occur when the engine firstbeginsto operate under its own power, as a result of admission of too much ,air which might-take place if the-suction passage to the bellows were not-controlled. When the valve in the suction passage is suitably-adjusted, the time required .to-build up sufficient suction in the bellows can ,be controlled so that the air valve will not be opened too. quickly.

In th device disclosed in the prior application, a metering valve was disclosed which controls the suction passage communicating with the cylindex in which a piston slides which operates the air valvein much the same way as does the bellows disclosed in this application, but such valve in theearlier case was controlled entirely by tem perature, This valve was only partially successful in eliminating the dimculties presented under variable operating conditions, whereas the manually adjustable valve provided according to this invention can be so set at any time as to take care ofsuch difiiculties as may arise.

As indicated previously, means are provided to operate the valve 22 in such manner as to enrich the mixture during the acceleration period. Inorder to accomplish this purpose, the shaft 50 has secured theretoinside the housing 5| of the control unit, an arm 15, one end of which is pivotallyconnected to a piston M slidable in a cylinder 16 formed in the control unit housing. The upper part of the cylinder i3 is connected by a passage 8 with a cylinder 88 which is also formed in the housing of the control unit adjacent the cylinder 76. The cylinder 80 communicates at its lower end which is closed by a metallic plate 82 with a suction passage 84 which communicates with the passage 66 previously mentioned and throughthis passage with the manifold. A piston 85'is slidable within the cylinder 80 and is normally held in its upper position as shown in the drawings by a spring 88 which i received between the piston and a washer 89 which rests on the metallic closure plate 82 in the lower end of the cylinder.

The piston -14 i provided with a port 9i) which is normally closed by a valve 92 held in closed position by a spring 94 the purpose of which will be apparent from the following description of the operation of this mechanism. Obviously, downward motion of the piston M will move the arm 10in a-counterclockwise direction. This arm being secured to the shaft 59 will rotate the shaft and through the medium of the connection between such shaft and the valve 22 moves the latter toward closed position. When the suction is relatively high in the manifold this high suction communicates to the cylinder 80 below the pistori'BB therein and pulls the piston downwardly toward the bottom of the cylinder. The piston ":is occupying some position in the cylinder 16 which is determined by the lifting eilect of the bellows and the action of the thermostat on the shaft 50. If it be assumed that from some given position of the throttle the latter is suddenly opened to increase the engine speed, the vacuum in the manifold will immediately drop and this reduction in suction below the piston 86 will permit the spring '88 to move such piston upwardly and through the medium of passage 18, will create a positive pressure in the cylinder '56 above the ,piston 14 "to 'forcethedatter downwardly :and

move the valve 22 toward closed position as described. As the engine picks .up;speed the ;suction in-the manifold will increase-to-some extent which will result in some motion of the piston :86

downwardly, relieving the pressure above, thepiston M and the efiect of the thermostat andzbellows brings about a motion of the arm 10 upwardly-to partly open the valve following the temporary closing movement just described.

The purpose of the valve 92 is to prevent the increase in suction, which takes place in the cylinder l6 as the suction in themanifoldincreases, from exerting a force on the piston 14 tending to lift such piston and through the piston to open the air valve. In other words, it is.desired that the entire effect of the suctionto open the valve 22 will be brought about by the bellows and not by the piston Hi. If it were not for this check valve, 'any'increase in suction 'in the space above the piston 14 due to downward movement of piston 86 would tend to lift the piston M, and

Formed in the wall of the cylinder "16 is a ta pered slot indicated by the reference character 86 which is provided for the purpose of'securing he degree of closing movement of the valve;22 during the acceleration'period in accordance with the particular conditions of operation which may prevail at the time the throttle is opened to bring about such acceleration. It has been found that the degree of enrichment of the mixture which is necessary during the acceleration period varies considerably depending upon the conditions of operation when the acceleration is efiected. For instance, if the temperature of theengine is high and if the engine speed is quite high when the acceleration takes place, less mixture enrichment is necessary than when the engine is cold, or is running slower.

In order to effect this difierence in the amount of enrichment for different conditions, the tapered slot is provided to permit a flow of air past the piston 14 under certain conditions and to vary this flow of air in accordance with the position of the piston in the cylinder when the pressure is created above such piston by the upward movement of the piston 86. For instance, if 'the piston 74 is occupying a position near the bottom of the cylinder 16 when the throttle is opened and the increase in pressure in the cylinder-16 above piston 14 takes place, the movement of'the piston should and will be relatively greater for the same increase in pressure above such piston than if the piston 1G is occupying a higher position in the cylinder 16 when the throttle valve is opened with a resulting increase in pressure above such piston 14. Obviously, when the piston M is near the top of the cylinder 16 there is -a greater leakage of air permitted past the piston through the tapered slot 96'than if the piston 14 is nearer the bottom of the cylinder and when inderllfi is such that when the thermostat is fully expanded and the valve 22 is wide open, the piston 1.4 is above this point of communication. a

This construction is provided because it is. not desired to bring about any. closing movement of the valve 22 following opening movement of the throttle when the throttle is nearly, wide open,

or when the temperature and suction conditions are such that the valve 22 has been moved to its wide open position by the action of the thermostat and the suction operated means. The. closing movement of the valve v22 is not necessary under tionbeing invited to-Figs. 3 and 8, that the suction passages which lead to the-bellows and to the cylinder 86 are joined in the wall of the hous-= ing 52 and form a single passage which communicates with a corresponding passage in the wall of the heating chamber which extends to the intake passage as shown in Fig. 3. The previously described suction passage 66 is formed in a removable cover plate I which is adapted to be se cured to the main housing 52 by screws orother suitable means and as pointed out previously, the

manually operable needle valve is positioned in this horizontal passage 65 as clearly shown in Fig.3. This valve maybe adjusted to ant desired position and located in position by a lock nut I02. I Communicating with the passage 66 ad jacen-t-the valve is a short vertical passage I04 also formed inthe cover plate I00 which connects with a passage I06 in' the vertical Wall of the housing i and in turn connects with a horizontal passage I08 also in the wall of the housing- 5|.

. Passage IE8 communicates with a passage I09 in the wall of the heating chamber which-extends to a space III] between the wall of the heating chamber and a metal gasket I I I, hereinafter described. Extending through the wall of the heating chamber and connecting the space IIO with' theintake pa'ssageis a restricted-tube I I3. Also communicating with the vertical passage I56 is the passage'84 previously mentioned, which communicates with the lower portion of the cylinder 80. Byconstructing the suction passages in this manner, all of these passages are formed by'drilling'in the walls of the unit and the useof flexible tubes is avoided which assists in the prevention of leaks and breakage of the tubes, and forms a much superior construction.

The space I I0 forms a sump in the suction line to thebellows which is provided for the following reasons. ing an opening movement of the throttle, there is a surge of'mixture through the suction passagetoward the bellows. This fuel mixture; particularly if ethyl gasolines are used as fuel, is likely to form a film of precipitation on the valve and other portions of thesuction passage. The space IIIJ forms a chamber or sump in which the liquid fuel content 'of the mixture is vaporized so that such a film is not formed on the valve and the passage wall with which thevalve coop-' erates.

stat directly on the wall of the heating chamber Upon reduction of suction followis determined by the effect of suction "on the bellows which may be great enough underpart throttle operating conditions 1 to move the valve the thermostatls positioned in. close. iproximity to theheating chamber which ismaintaine'd at the desired temperature to-control the. expansion l ofthethermo'stat. .1 It has. been found that by controlling the thermostat. in this w'ayitsopen ation is such as to provide a .mixtu'reo'f; more nearly the proper fuel air. ratio. than can-be. secured if the thermostat is remote; from the heating chamber andmeans are providedto C011: duct exhaust gas from .theexhaust manifold .to

heat the thermostat or to provide a heating .means of other form. i

Secured .between the control unit of the heating chamber is a copper or otherlmetal l gasket I.I2 which is projected outwardly toward the thermostat at land is provided .with an extending portion mostatic coil. This gasketserves as .a positive such air as maybe admittedtothe chamber. in

the housing 52 in which the thermostatic coil is positioned. By the provision of this gasket and heat conducting. shield, it has been found that the operation of the thermostat is much improved and less variable than ifssu chi means isnot provided. i

It may be here noted-that the control' unit is provided with a removable bottom plate I'I'I in which orifices H9 for the .admission of. air are Iformedq These orifices are covered by a porous washer I2I, secured betweena shield I23 also having orifices I25.correspondingto orifices H9 in the bottom plate, this assembly being secured together by a rivet I21. i Adjustable means are provided to throttle operating conditions when I the valve 22 is not fully opened by the thermostaathat is when the engine temperature is not high enough to cause the thermostat to open the valve 22 to a wide open' position and the position of the valve 22 to such a wide open position as to form too lean a mixture for satisfactory operation.

For accomplishing this result, the link 54 at its lower end has a horizontal portion I20 which supports integrally therewith, or in any other suitable manner, a fiat surface I22 which is adapted to engage a stop cam I24 as the bellows contracts and the link 54 is lifted; The cam I24 liesin .the pathofmovement of thesurfac e I22 and is secured in any suitable manner-to the inner end of a stud I26 which is provided with a reduced portion I28 received in anorifice in the wall of the housing 5| to ipermit rotation of theistu'd carrying the cam. Outsidethe' housing 52 there is secured to the stud an indicating plate I30, by means of which the stud can berotated' and is held many set position by screw I32 asshown in Fig. 5.. The cam is so shaped when th'e plate I30 is set in diflerent positions, it'will varithe. sense of positively. stopping? the movement of link 54 referred to.

I I5. which extends partly s around the thermostat and also end portions I I8 which project adjacent the ends ofthe therlimit the up-= ward movement of; the bellows under the infiu ence of suction for the purpose of variablycontrolling the richnessof the mixture-underpart The relative arrangement of the thermally: re sponsive means and suction operated" means .with

' respect to the operating. linkwhich extends: to

the air inletvalve have been modified in-con-. struction and. improved. in function... In'the earlier application the suction operated element corresponding to the bellows 60 is connected to' a rigid arm secured to the shaft. to which one end of the thermostat is. connected. while the;

. free end of the thermostat is connected. to the 10 link. which extends to the? valve operating. arm corresponding to the arm 44. This construction necessitated bringing the link corresponding to the link46 into the space within-the housing of the control unit, since: the thermostat must, l5 obviously, be. positioned within theunit. Such a construction presentedcertain difficulties, manufacturing and otherwise, which are overcome bythepresent construction,..in whichthe free end of the thermostat'is connected directly to thesuction operated element, and the shaft-to which the. other. end of: thethermostat is connected has anoperating arm'. thereto outside the ,housing which is connected directly to the 'valve operatingi arm 44. Thismodified arrangement is a' m minor:improvement* structurally, but its practi cal advantages ;are' relativelyimportant.

It has been-found that. when an automaticchoke mechanism is. employed, it is desirable. to provide. what is termed a fast idle! device, that is, a means for causing the engine to rotate faster whenidling. cold than what is considered anormal or hotidlingspeed. Sucha device-1's desirable to prevent stalling of. the engine after it commences to. run underitsown power. when .35.". cold. It isequally obvious that;under normal; conditions, as whenthe. engine, temperature is 1-. relatively high, so'high an.idling;speed is-understandabla- Therefore, in'accordance with the present invention, meanshavebeen provided: to 40kt variably. control the idling speed for-different: conditions of operation, such speed being con-= trolled by the position of the choke.

The idlingspeed of the, engineis, regulated by; providing a stop to-limit the. movement either throttletoward. closed position- Referring toFigz. 1,.the numeral Iindicatesthe-throttle operatinglink, which is adjustably connectedin any; suitable way to a .throttlei operating arm.-.I52=.se-:* cured to the throttle shaft. This :arm carries -a.--. stop screw I54 held in position: by a lockfscrew: I56 andadapted to engagesa graduatedstop cam I58 which is-formed with three stop surfaces I59;v IBM and I59b, this cam being. positioned. by the choke controlling mechanism. 7

It will be .notedupon examination of. Fig. '7 that the shaft 50 to which the thermostatissee cured is j ournalled atone end in anut IBUscrewed: into the housing, .1 This-nut is provided with ac, projecting hubsportion I62 on which, the stop camlmo I58 is journalled. The operating lever 48 to which the operatinglink for thechoke valve 22 is con-: nected has axlaterally projecting ear I64 whichzz overlies ,a projecting toe I66 formed on..thestop,ic cam. A set screw I58 adapted.toengage'theatoe:6o I66'is screwed intothis ear'andtis. providedwithi. a lock nut I10 between which and, the ear, is; clampedzone; end of a: U-shaped flat spring: the: other end of which ext'endsaround and below the. toeon the idle stop.

" Obviously, Withthearrangement disclosed, the; idlestop is .moved positively toward thepositiom shown in Fig. l, as. the valve-22 is moved toward} closed-position. by.v engagement of the screw; I682 with the toe of the; stop.-=cam-.- .In..this...positioni7q aerator the surface I 59 engages stop screw I54 to hold the throttlevopento an appreciable extent for fast;- idling. The-purpose of spring I12 'is to'permit the:

choke control lever 48 to move toward the open position as the engine warms up on idle or during: our :tiinedvacuum. take .01? which would otherwise a be prevented by the pressure of the idle screw I 54 on caml58 due toiorce of fthrottle return-spring. Otherwise theaengine would get too rich if the throttle was not openedduring warmup.

As. the valve. 22. moves. toward open position": uponan increase in temperature, thestop cam is yieldingly moved by action .of'.the. spring IIZ so as:

to successivelybring the stopsurfaces I59a'and I592) into position to: engage the. screw? I 54=so asto permitthe throttle to move toamorenearly' closed position for idling: as the choke-valveis;

moved to a more nearly open position.

Particular attention is directed .to the fact that the stop; cam :is .journalled orrthe hub of the nut IGl'Minsteadof being'journalledon the shaft 50.

The purpose of .thisconstructionis to prevent the pressureof the: throttle: closing: spring which is exerted againstitherstop, cam, from causing. frictional"resistance:to.the motion of the shaft.50',. which must be free to move under: the influence ofthecontrol unit in order that the mixture ratio be maintained accurately in the proportions de* sired.

While the embodiment of the present invention as herein disclosed, constitutes a preferred form, it isto be'understood that other forms might be adopted, all coming within the scope of the claims which follow.

Whatis claimed is as follows:

1; An automatic choke mechanism for the:

charge forming. device of, an. internal combustion.

engine having an intake manifold provided with a heating chamber for heating the combustible mix-. ture supplied to the engine, and comprising, in combination, a. mixture:proportioningv means; a control unit for operating said mixture proportioning means and including a'housing, thermally,

responsive'means in said housing-adapted to op-- erate. the mixture proportioning means, suction operated element adapted to move the mixture: 'proportioning means,- and adjustable means to limitthe movement of said. suction operated.v means in one direction of movement, said means: comprising an angular'member. connected .to the. suction operated; element and an adjustable-stop member engaging said angularmemben 2; An automatic choke mechanism. for the charge formin device of an internal combustion engine having an. intake manifold provided with arheating chamber. for' heating the. combustible mixture supplied .to the.-engine, and. comprising,.

in combination, a mixture proportioning'means, a

control unit for operating; saidmixture proportioning means andincludingahousing, thermally responsive means in :said housing; adapted: to.-op.- erate the mixture proportioning means, .suction operated element adapted to move the=-mixture= proportioning means toward-positiontolean the? mixture upon increase of suction; andadjustable: means .to limit the movement of said. suction operated element as the'suction-increases, whereby the mixture proportions when operating withiapartly open throttle can be determined, saidmeans comprising anangular member connected: to the suction operated-elementandan adjustable. stop memberrengaging saidrangular member;

3. An automatic choke mechanism for. then charge forming device of: an internal. combustion enginehavinggan intake manifold'provided' with aheating chamber forheating the combustible, mixture supplied to the engine, and comprising, in combination, a mixture proportioning means, a,

controlunit for operating said, mixtureproportioning means and includinga housing, thermally responsive means in said housingadapted to opcrate the mixture proportioning means, a suction operated member adapted to move themixture proportioning means toward position to lean the mixture, a stop carried bysaid suctionoperated membensaid stop being an angular element depending from the bottom of said suction operated member and a manually adjustable element movable in'the path of movement of said angular element for variably limiting the movement of said suction operated element upon increase of Sue'- tion.

5!. An automatic choke mechanism for the charge forming device of an internal combustion engine having an intake manifold provided with a heating chamber for heating thecombustible mixture supplied to the engine, and comprising, in combinatioma mixture proportioningmeans, a control'unit for operating said mixtur proportioning means and including a housing, suction operated means'in said housing adapted tov operate said mixture proportioning means, a suction passage leading to said suction operated means from the engine intake passage and a chamber in said suction passage adjacent the heating chamber adapted-to act as a vaporizing-device for any combustible mixture which may enter the by the ,charge forming" device to the. engine a shaft operable in accordance with engine temperature and suction conditions for determining the position of said mixture proportioning means, anda stop member supported on and operable by said shaft for variably determining the closed or idle position of saidthrottle.

6. An automatic choke mechanism for the charge formingdevice of an internal combustion engine having an intake manifold provided with a heating chamber for heating the combustible mixture supplied to the engine, and comprising, in combination, a mixture proportioning means, a control unit for operating said mixture proportioning means and including a housing, a throttle for regulating the amount of mixture suppliedby the charge forming device to the engine, a, shaft operable in accordance with engine temperature and suction conditions for de termining the position of said mixture proportioning means, a nut screwed into said housing andforming a journal for said shaft, a hub extending from said nut, a stop member journalled on said hub and operable to variably dethrottle.

, '7. An automatic choke mechanism for the charge forming device of an internal combustion engine having an intake passage for supplying combustible mixture to said engine, and comprising, in combination, a mixture proportioning device adapted to control the admission of one of rn ine the closed or idle position of said the components to the combustible mixture supplied to the engine by said charge forming device, a' control unit for controlling the position of said mixture proportioning means including thermally responsive means operating said mixture proportioning means and adapted ,to be heated during operation of the engine, means re sponsive to variations in pressure in said intake passage for moving said mixture proportioning means toward a position to enrich the mixture upon acceleration of the engine and means for variably regulating the degree of mixture en-' richment produced by said last named means in accordance with the position of said mixture proportioning means at the time the acceleration of theengine begins.

8. An automatic choke mechanism for the, charge forming device of an internal combustion engine having an intake passage for supplying. combustible mixture to said engine, comprising, in combination; mixture proportioning device adapted to control the admission of one of the components of the combustible mixture supplied to the engine by said charge forming device, a control unit for controlling the position of saidv mixture proportioning means including thermally responsive means for operating said mixture pro-' portioning means and adapted to be heated dur-, ing operation of the engine, means responsive to variationsin pressure in said, intake passage for moving the mixture proportioning means toward; a position to lean the mixture when the engine starts to run, a second pressure responsive means for moving said mixture proportioning means toward a position to enrich the mixture upon. acceleration of the engine, and means for variably regulating the degree of mixture enrichment produced by said second means in accordance with the position of said mixture proportioning means at the time the acceleration of the engine begins.

: 9. An automatic choke mechanism for the charge forming device of an internal combustion engine having an intake passage for supplying combustible mixture to said engine comprising, in combination, a mixture proportioning device adaptedto control the admission of one of the components of the combustible mixture supplied to theengine by said charge forming device, a control unit for controlling the position of said mixture proportioning means including thermally responsive means for operating, saidmixture proportioning means and adapted to: be

heated during operation of the engine, means responsive to variations in pressure in said intake passage for moving the mixture proportioning means toward a position to'lean the mixture when the engine starts to run, a second pressure responsive means for moving said mixture proportioning means toward a position to enrich the mixture upon acceleration of the engine, means for variably regulating the degree of mixture enrichmentproduced by said second means in accordance with the position of said mixture proportioning means at the time the acceleration of the engine begins, and adjustable means for variably controlling the action of said first pressure responsive means.

10. An automatic choke mechanism for the charge forming device of an internal combustion engine having an intake-passage for supplying combustible mixture to said engine comprising, in combination, a mixture proportioning device adapted'to control the admission of one of the components of the combustible mixture supplied to the engine by said charge forming device. a

control unit for controlling Y the position of said mixture proportioning means including- (her-- really responsive means for operating said -mix=- ture proportioning means and adapted to be' heated-during operation of the engine, means responsive to variations in pressure insaid-intake passage for moving the mixtureproportioningmeans- -toward a position to-leanthemixt'ure when the engine starts to run, a second-pressure re sponsive meansfor moving said mixture propertioning-means toward a position toenrich-the mixture upon acceleration of the engine, means for variably regulating-thedegree of mixtureenrichment produced by said-secondmeans'in acco'rdance with the position of said mixture proportioning means at the time the acceleration-of the engine" begins, and manually adjustable means for variably controlling the action of said' first pressure responsive means.

11. An" automatic choke mechanism for the charge forming device of an internal combustion engine having anintake passage for supplying combustible mixture to said engine comprising,

in combination, a mixture proportioning device adapted to'control the admission of one of the components of the combustible mixture supplied to the engine by said charge forming device, a control unit for controlling the position of mixture proportioning means, including thermally responsive means for operating said mixture proportioning meansand adapted to be heated during: operation of the engine, means responsive to variations in pressure in said intake passage for moving the mixture proportioning means toward-a better position to lean the mixture when the engine starts to run, a second pressure'responsive means for moving said'mixture proportioningmeanstoward a positionto enrich the" mixture upon acceleration of the engine, manually operable means for variably controlling the action of the first'pressure responsive means and automatic means for variably controlling the" effectiveness of: the second pressure responsive" means.

12. An automatic-chokemechanism for the charge forming device of an intern'a1 combustion engine having" an intake passage for supplyingcombustible mixture to saidengine and compris-' ing, in combination, a mixture" proportiomn'g' device a'da'pteclto control the admission of one" of the: components of the combustible mixture supplied to the engine by said charge forming device, ascontrol unit for controlling the posit-ion ofsaid mixture proportioning means including thermally responsive means for operating said mixture proportioning means and adapted to be heated during operation of theengine, pressure responsive means operable upon reduction in pressure in the intake passageto move said mixture proportioning means towa'rd aposition to lean the mixture, another pressure responsive means operable upon anincrease in-pressure in the intake passage to move said mixture proportioning means toward a position to enrich' themixture and means for automatically varying the effectiveness. of said last named means-in accordance with the position of said means at the time it becomes effective.

13; An automatic choke mechanism for the charge forming device of an internal combustion engine having an intake passageforsupplying" fig s ri d to the efigine by said" charge forming device; a'-= c0 01 unit for controlling 'the position of said mixture proportioning:- means including then-'- mall y responsive means for operating said mix ture' proportioning means and adapted to be effectiveness of said first mentioned pressureresponswe device and means for automatically" varying the efiectiveness of said last named means in accordance with; the position of mixture proportioning means at the time said last" n'am'ed'means becomes effective. a V

14; automatic" chokemechan'ism for the" charge forming device of an internal combustion engine' h'aving an intakepassage' for supplying combustible mixture tosaid engine comprising,

- '-in combination, a mixture proportioning device adapted to control the admission of one of the components of the combustible mixture'supplie'd totheengine by said charge forming device, a" control unit for controlling the position of said mixture proportioning means including thermally responsive means'for operating said mixture" proportioning means and adapted to be heated during operation of the engine, a pressure re: sponsivedevice comprising a cylinder and a'pi's ton slidable therein and subject to variations in pressure in'the'intake passage for moving said mixture proportioning means toward a position to enrich the mixture and means for progressively increasing the effective pressure on said piston as the mixture proportioning means'i's' moved'toward'its' mixture enriching position.

15. An automatic choke mechanism for the charge forming device'of an internal combustion engine having an intake passage for supplying combustible mixture to said'engine comprising, in combination, a mixture proportioning"device' adapted to control the admission of one of the components of the combustible jmixture supplied to the engine by said charge forming devicela control unit for controlling the position of said mixture proportioning means including thermally responsive means for operating said mixt'ure' proportioning means and adapted to be heated during operation of the engine, a pressure responsive device comprising a cylinder and a pis' ton slidable therein and subject to variations in pressure in the intake passage for moving saidmixture proportioning means toward a posi sure in theintake passage for moving said mixture proportioning means toward a position to lea-n the mixture; manually operable means'for' regulating thepressure effective on said'secon'd" pressure responsive piston and means for pro gressively increasing the eiTective pressure on saidpiston asthe mixture proportioning means is-*moved toward itsmixture enriching'position';

16. An automatic choke mechanism for the charge-forming device of an internal combustion engine having an intake passage for supplying combustible mixture to said engine comprising; incombination, a mixture proportioning device adapted to control the admission of one of tlie" 76" components: ofiith'e combustible "mixture-supplied to' the engine, by said charge forming device, a control unit for controlling the position of 1'7. An automatic choke mechanism for the charge forming device of an internal combustion engine having an intake passage forsupplying combustible mixture to said engine and comprising, in combination, a mixture proportioning device adapted to control the admission of one of the components of the combustible mixture supplied to the engine by said charge forming device, a control unit for controlling the position of saidmixture proportioning means including thermally responsive means 'for operating said mixture proportioning means and adapted to be heated during operation of the engine, a pressure responsive device comprising a cylinder and a piston slidable therein and subject to variations in pressure in the intake passage for moving said mixture proportioning mean toward a position to enrich the mixture, and a slot in the wall of the cylinder adjacent the piston, said sure efiective on the piston.

18. An automatic choke mechanism for, the

charge forming device of an internal combustion engine having an intake passage for supplying combustible mixture to said engine comprising, in combination, a mixture proportioning device adapted to control the admission of one of the components oi the combustible mixture supplied to the engine by said charge f orming device, a control unit for controlling the position of said mixture proportioning means including thermally responsive means for operating said mixture proportioning means andadapted to be heated during operation of the engine, a pressure responsive device comprising a cylinder and a piston slidable therein and subject to variations in pressure in the intake passage for moving said mixture proportoning means toward a position to enrich the mix ure, and a'slot in the wall of the cylinder adjacent the piston of progressively increasing cross sectional area wherebythe pressure effectivelonsaid piston is reduced as said piston moves toward the larger end of said slot.

1 9. An automatic choke mechanism for the chargeforming device of a n'internal combustion engine having an intake passage for supplying combustible mixture to said engine comprising, in combination, a mixture proportioning device adapted to control the admission of one of the components of the combustible mixture supplied to the engine by saidlcharge forming device, a control unit for controlling the position or said mixtureproportioning means including thermally responsive means for operating said mixture proportioning means and adapted to beheateddury ing operation of the engine, a pressure responsive device comprising a cylinder and a piston slidable thereinand subject to variations in pressure in the intake passage for moving said mixture pro portioning means toward aposition .to enrich the mixture, a second;pressure responsive member;

subject to variations in pressure in the intake passage for moving said mixture proportionin'g means toward a position to lean the mixture, a conduit for communicating the pressure of the intake passage to said second pressure responsive member, a valve in said conduit for controlling the effective pressure on said second pressure responsive member as desired, and a pressure by-pass comprising a slot in the wall of said cylinder adjacent the piston and of varying cross sectional area, for variably controlling the pressure effective on said piston ,as the latter moves to different positions.

20. An automatic choke mechanism for the charge forming device of an internal combustion engine having an intake passage for supplying combustible mixture to said engine comprising, in combination, a mixture proportioning device adapted to control the admission of one of the components of the combustible mixture supplied to the engine by said charge forming device, a control unit for controlling the position of said mixture proportioning means including thermally responsive means 'for operating said mixture proportioning means and adapted to be heated during operation of the engine, a pressure responsive device comprising a cylinder and a pistonslidable therein and subject to variations in pressure in the intake passage for moving said mixture proportioning means toward a position to enrich the mixture, a slot in the wall of the cylinderf or controlling the' pressure effective on thepiston, and

, a second pressure responsive member also subject to variations in pressure in the intake passage for ,moving'said mixture proportioningdevice toward'a position to lean the mixture.

21. An automatic choke mechanism for the charge forming device of an internal combustion engine having an intake passage for supplying combustible mixture to said engine comprising, in combinatiom'a mixture proportioning device adapted to control the admission of one of the components of the combustible mixture supplied to the engine by said charge forming device,'a control unit for controlling the position of said mixture proportioning means including thermally responsive meansfor operating said mixture proportioning means and adapted to be'heated during operation of the engine, pressure responsive means subject to variations in the pressure in the intake passage operable to move said mixture proportioning means toward a position to enrich the mixture upon an increase in pressure, means for, automatically varying the eifective pressure on said last namedm'ans in accordance with the position of the" mixture proportioning means, another pressnreresponsive means subject to variations in'pressure in the intake passage and operable to .move said mixture 'proportioning means toward a position to lean the mixture upon decrease of pressure and means to control the efiectiveness of said last named means independently of the" position of said mixture proportioning means; I

22. An automatic choke mechanism for the charge forming device of arrinternal combustion engine having an intake passage for supplying combustible mixture to said engine comprising, in combination, a mixture propor'tioning device adapted tocontrolthe admission of one of the components of, the combustible' mixture supplied to the engine by said charge iorming device, a' control unit for controlling the position-of said mixture proportioning means including thermally responsive means for operating said mixture proable to move said mixture proportioning device toward a position to lean the mixture upon a decrease of pressure in the intake passage and means for controlling the effectiveness of said device independently of the position of said mixture proportioning means;

23. An automatic choke mechanism for the charge forming device of an internal combustion engine having an intake passage for supplying combustible mixture to said engine comprising, in combination, a mixture proportioning device adapted tocontrol the admission of one of the components of the combustible mixture supplied to" the engine by said charge forming device, a control unit for controlling theposition of said mixture proportioning means including thermally responsive means for operating said mixture proportioning means and adapted to be heated during operation of the engine, a pressure respon'sive device subject to variations in pressure mixture proportioning means toward a position to enrich the'mixture upon an increase in pres' sure, said device comprising a cylinder and a'pis-' ton'slidable therein and operatively connectedto the mixture proportioning means,'a slot in the wall of the cylinder adjacent the piston and extending in 'a'direction parallel to'the path of movement of the piston, said slot being of vary ing' cross sectional area throughout its length and operative to vary the pressure effective on said piston as the piston moves to different posi'- tions'in the cylinder, a secondpressure respon-- sive device subject to variations in the pressure in the intake passage and operable to move the mixture proportioningfdevice toward a positionto' lean the mixture upon a decrease in pressure and a valve operable to control the effectiveness of said second sired.

24. An automatic choke mechanism for thecharge forming device of an internal combustion engine having an intake passage for supplying combustible mixture to said engine, comprisin in combination, an air choke regulating admis-' sion of "air, a control unit for operating said choke valve including a thermally responsive device adapted to be heatedduring operation of theengine, means responsive'to variations in pressure in said intake passage'for'moving said choke valve toward closed position upon ac celeration of the engine and meansfor variably regulating the movement of said valve in ac-- cordance with the position of the valve at the beginning of such movement.

' 25. An automatic choke mechanism for the charge forming device of an internal combustion engine having'an intake'passage for supplyingcombustible mixture to said engine, comprising; in combination, an air choke regulating admission of air, 'a' control 'unit for operating said choke" valve including a thermally-responsiv device "adapted to be heated during operation of the engine, meansresponsive to variations in pressure responsive device as de pressure insaidintake passage for moving: said chok'e valve towardclosed position upon acceleration oi the engine, means for variably regulating the movement of said valve toward closed position in accordance with the position of the valve at the beginning of such movement,

in combination, anair choke regulatin admission of air, a cont-rel u iiit for operating saidchoke' valve including a thermally" responsive d'evice adapted robe heated during operation of the:

engine, mean operable tomov'e said choke valve toward closedposition upon an increase pressure to enrich the mixture, s'aid means comprising a member operatively connected to the valve and subject to variations in pressurein the iii-- take passage,- means for variably controlling thepressure eiiecti'veon said member in accordance with the position ofsaid choke valve, a second pressure responsive means operable upon de-' crease of pressure in the intake passage to movesaid choke valve toward open 'csitionand means for controlling the effectiveness of Said last namedmeans independently of the positionof said choke valve.

-2-7. An automatic choke mechanismfor the charge forming deviceofi an internal combustion engine provided with a heating chamber adapted to be heated by exhaust gas comprising, in com bination, a mixture proportioning means, acontrol unit for controlling the position of said'mix tureproportioning means, and including a housing, a thermally responsive element in said hous ing and adapted to operate the mixture proportioning means, means for securing said housing to the wall of the heating chamber anda metallic heat conducting element secured between the housing and heating chamber and extending toward and around said thermally responsive element on threesides of the latter to conduct heat from the heating chamber to saidthermally responsive element;

28. An automatic choke mechanism for the charge forming device of an internal combustion engine provided with a heating chamber adapted to be heated by exhaust gas, comprising, in combination, a mixture proportioningmeans, acontrol unit for controlling the position of said mix tu're proportioning means and including a'housing, a thermally responsive element in said-housing and adapted to operate'the mixture roportioning means, means for securing said housing to thewall of the heating chamber, a pressure responsive member also effective to operate said mixture proportioning means, a heat conduct-- ing element secured between-said-heating chamber and the housing and extending toward the thermally responsive element to conduct heat thereto, said heat conducting element being so constructed as to form a chamber between itselfand the wall of the heating chamber; conduits connecting said chamber with the intake passage and-th pressure responsive member respectively, whereby said chamber formsa' part of the passage which communicates the pressure of the intake passage to said pressure responsive element.

29; An automatic choke mechanism for the charge forming device ofan internal combus tion engine provided with a heating chamber adapted to be heated by exhaust gas comprising, in combination, a mixture proportioning means, a control unit for controlling the position of said mixture proportioning means, and including a thermally responsive element adapted to operate the mixture proportioning means, a pressure responsive means also efiective to operate said mixture proportioning means, and a passage for communicating the pressure of the intake passage to said pressure responsive means, said passage having a closed, enlarged chamber formed therein to form a reservoir for any fuel which may collect in said passage.

30. An automatic choke mechanism for the charge forming device of an internal combustion engine provided with a heating chamber adapted to be heated by exhaust gas, comprising, in combination, a mixture proportioning means, a control unit for controlling the position of said mixture proportioning means, and including a thermally responsive element adapted to operate the mixture proportioning means, a pressure responsive means also efiective to operate said mixture proportioning means, a passage for communicating the pressure of the intake passage to said pressure responsive means, said passage having a closed, enlarged chamber formed therein to form a reservoir for any fuel which may collect in said passage, and means for heating said chamber to vaporize any fuel collected therein.

31. An automatic choke mechanism for the charge forming device of an internal combustion engine provided with a heating chamber comprising, in combination, a mixture proportioning means, a control unit for determining the position of said mixture proportioning means including a thermally responsive means, a shaft operated by said thermally responsive means and operatively connected to said mixture proportioning means, a throttle forregulating the movement of mixture supplied to the engine, a

stop member carried by said shaft and operable thereby to variably determine theclosed or idle position of the throttle, and means permitting movement of said shaft relative to the stop member.

32. An automatic choke mechanism for the charge forming device of an internal combustion engine provided with a heating chamber, comprising, in combination, a mixture proportioning means, a control unit for determining the position of said mixture proportioning means including a thermally responsive means, a shaft operated by said thermally responsive means and operatively connected to said mixture proportioning means, a throttle for regulating the movement of mixture supplied to the engine, a stop member rotatably supported on said shaft, means for positively connecting said stop member with the shaft for rotation therewith when, the shaft is rotated in one direction and means for yieldingly connecting the stop member with said shaft when the latter is rotated in the opposite direction.

33. An automatic choke mechanism for the charge forming device of an internal combustion engine and comprising, in combination, a mixture proportioning means, a control unit for positioning said mixture proportioning means and comprising a housing, thermally responsive means for operating the mixture proportioning means, means for heating said thermally responsive means when the engine is operating, means responsive to variations in pressure adapted to move the mixture proportioning means toward position to enrich the mixture during the acceleration period and means for variably regulating the degree of mixture enrichment produced by said last named means in accordance with different operating conditions which may occur at the time such mixture enriching means becomes operative.

CLARENCE H. J ORGENSEN. 

